The present invention relates to a thrust reverser for a turbojet engine having a thrust reverser baffle movable to the rear of an engine cowling assembly to redirect gases emanating from the cowling into a reverse thrust direction.
Turbofan-type turbojet engines are well known in the art and typically comprise a fan at the front of the turbojet engine which directs a flow of bypass air through a duct bounded by the engine cowling on the inside and a fan cowling on the outside. The generally annular duct bounded by the engine cowling and the fan cowling may channel both the bypass flow and the primary exhaust gas flow at a downstream portion from the turbojet engine, or may channel only the bypass flow.
In aircraft on which the turbojet engine is mounted outside of the airframe structure, the fan cowling and the engine cowling are configured to form boundaries of the bypass flow duct and to provide aerodynamic outer surfaces to reduce drag.
FIGS. 1 and 2 illustrate a known pivoting door-type thrust reverser associated with the cowling of a turbofan-type turbojet engine. As illustrated in FIG. 1, the upstream portion of the cowling which defines the outer limits of the bypass flow duct and which is generally concentrically arranged about the turbojet engine (not shown) is designated as 1 and generally comprises an external cowling panel and an internal cowling panel interconnected by a frame 6. The outer surface of the external cowling panel has an aerodynamic surface over which the air external to the engine passes during aircraft flight. The inner surface of the inner cowling panel defines the outer boundary of the bypass flow duct through which the bypass flow passes in the direction of the arrow.
The cowling also comprises a thrust reverser 2 and a downstream cowling portion 3. The thrust reverser 2 comprises a door 7 pivotally attached to the cowling so as to pivot about a transverse axis such that it is movable between a closed, forward thrust position, illustrated in FIG. 1, and an open, reverse thrust position, in which the forward end (towards the left as viewed in FIG. 1) of the thrust reverser door 7 is moved outwardly from the cowling, while a rear portion is moved inwardly into the bypass flow duct so as to redirect at least a portion of the bypass flow through an opening in the cowling in a direction that has a reverse thrust component.
A known actuator 8 for moving the door 7 between its forward thrust and reverse thrust positions may comprise a hydraulic cylinder extending through and mounted to the frame 6, and having an extendible and retractable piston rod connected to the thrust reverser door 7.
The thrust reverser door 7 has an outer panel 9, an inner door panel 11 and the forward end of the door 7 may have a deflector to maximize the efficiency of the thrust reverser when the door 7 is in the reverse thrust position. The inner surface 11 tapers toward the outer surface of the door 7 at the forward end of the door, forming a cavity when in the forward thrust position.
A plurality of thrust reverser doors 7 may be incorporated into the cowling, such doors being circumferentially spaced around the periphery of the cowling as illustrated in FIG. 2. A portion 18 of the cowling extends axially between a forward part 4 and a rear part of the cowling adjacent thrust reverser doors 7 to provide structural rigidity to the cowling and to provide pivot mounting points for attaching the doors 7 to the cowling. French Patents 2,618,853; 2,618,852; 2,621,082; 2,627,807; 2,634,251; 2,638,207; and 2,651,021 illustrate typical, known thrust reversers.
In some applications, installation of a known type of thrust reverser raises substantial difficulties and may, for all practical purposes, be impossible. These difficulties arise in turbofan engines having a very high bypass ratio and which incorporate a fan cowling having a short axial length compared to the axial length of the jet engine cowling. In these instances the use of such an axially short fan cowling produces a relatively short bypass flow duct and renders the use of such known type of thrust reversers virtually impossible.
French Patent 2,722,534 discloses a thrust reverser for a turbofan type turbojet engine attached to the cowling assemblies by linkrods. This known design entails the drawback of positioning a downstream or rear linkrod in the acceleration zone of the gas flow inside the bypass flow duct and, in particular, in a zone where the linkrod pivots on the jet engine cowl. Since the speed of the gas flow is close to, or exceeds the speed of sound during aircraft cruising flight, the location of this linkrod causes substantial aerodynamic disturbances. Moreover, further aerodynamic losses are caused by notching or embossing the thrust reverser baffle or the associated fixed cowling structure to allow the displacement of the rear linkrod during movement of the baffle between the forward and reverse thrust positions. Another drawback is caused by stops which must be mounted on the engine cowling structure to retain the rearmost edge of the thrust reverser baffle on the engine cowling when the baffle is in the reverse thrust position. Consequently, when the baffle is moved to the forward thrust position, these stops project beyond the engine cowling surface causing further aerodynamic disturbances.